Plasma deposited optical waveguide

ABSTRACT

An optical element, such as a waveguide, is formed by utilizing a plasma deposited precursor optical material wherein the plasma deposition is a two-component reaction comprising a silicon donor, which is non-carbon containing and non-oxygenated, and an organic precursor, which is non-silicon containing and non-oxygenated. The plasma deposition produces a precursor optical material that can be selectively photo-oxidized by exposure to electromagnetic energy in the presence of oxygen to produce photo-oxidized regions that have a selectively lower index of refraction than that of the non-photo-oxidized regions whereby transmission of a light signal through selected non-photo-oxidized and photo-oxidized regions can be controlled. Subsequent photo-oxidation or variable photo-oxidation can be used to produce various discrete regions with different indexes of refraction for fabrication, optimization or repair of photonic structures.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.09/435,396, filed Nov. 6, 1999, now U.S. Pat. No. 6,416,938 which is acontinuation-in-part of U.S. application Ser. No. 08/873,513, filed Jun.12, 1997, now abandoned, which claims the benefit of U.S. ProvisionalApplication No. 60/020,392, filed Jun. 25, 1996.

FIELD OF THE INVENTION

The present invention relates to an optical element, such as an opticalwaveguide, and more particularly to an optical element fabricated fromthe selective photo-oxidation of a material formed by a plasma-initiatedpolymerization from a two-component reaction.

BACKGROUND OF THE INVENTION

A basic optical signal channel comprises an optical information channel,which for a guided channel, can generally be referred to as a waveguide.The waveguide conducts an optical signal from a first optical componentto a second optical component. The optical signal may be light of asingle frequency (or color), or may be a multiplexed combination ofoptical signals of different frequencies in a wavelength multiplexingscheme.

When the waveguide is formed as part of an integrated circuit on amicrochip for transmission of the optical signal between components, theon-chip waveguide may be formed as a free-space optical path, or morecommonly, a photolithographically produced waveguide core material thatis surrounded by boundary materials, or cladding. A boundary materialhas an index of refraction (IOR) that is different from (generallylower) than the IOR of the core. With appropriate selections of IORs forthe core and boundary materials based on the frequency characteristicsof a particular optical signal, the signal is transmitted through thewaveguide core material.

A typical cross section of a basic on-chip waveguide 10 is illustratedin FIG. 1. Core material 12 is surrounded by one or more types ofboundary materials which, in this example, are identified as bottomboundary material 14, top boundary material 16 and side boundarymaterial 18. Core material 12 is the optical waveguide material throughwhich a light signal is transmitted. The difference between the IOR ofcore material 12 and the boundary materials can be as small as 0.001 fora functional optical waveguide. Further the state of the top and bottomboundary materials is not limited. A boundary material may be in thegaseous, liquid or solid state, as long as the material satisfies thedifferential IOR relationship between boundary materials and the core topermit optical waveguiding. While it may be advantageous for lightpropagation symmetry to have the IOR of the bottom and top boundarymaterials equal to the IOR of the side boundary material, it is notnecessary, as long as the IOR of all boundary materials is lower thanthe IOR of core material 12. FIG. 1 also shows a substrate 20 upon whichbottom boundary layer 14 is disposed. In other applications thesubstrate itself may be the bottom boundary layer. For further referenceto conventional on-chip optical waveguides see the Handbook ofPhotonics, Gupta, Mool C., editor-in-chief, CRC Press LLC, Boca Raton,Fla., 1997.

Conventional on-chip optical waveguides are formed from either organicor inorganic materials using conventional integrated circuit fabricationand patterning techniques. While these materials, such as silicondioxide and quartz, are similar to those used in a fiber optic cable,light signal transmission losses through an on-chip waveguide isconsiderably greater than those experienced through an optical fiber.Light wave propagation losses in an optical waveguide are typically fromtwo sources. The first is optical absorption, or scattering, in the bulkof the waveguide material, while the second is interface scattering fromthe light interaction with the walls of the waveguide. The conventionalfabrication technique for the waveguide core, which requires a blanketlayer deposition of a material and subsequent selective removal of thematerial by photoresist patterning and wet, or dry, chemical etching,results in wall damage of the core that increases the core-boundarymaterial interface scattering losses.

In a conventional process for forming waveguide 10, as illustrated inFIG. 2( a) through FIG. 2( f), waveguide base material 22 is blanketdeposited on bottom boundary material 24, which in this example, alsoserves as the substrate. Photoresist 26 is deposited on waveguide basematerial 22 (FIG. 2( a)). Photoresist 26 is typically a spun-on organicmaterial that completes crosslinking with selective exposure toultraviolet (UV) light through a mask 60, and subsequent baking (FIG. 2(b)). Photoresist 26 is selectively developed to leave a photoresist mask61 over the desired waveguide core, while the remainder of photoresist26 is etched away by a conventional etching method (FIG. 2 (c)). Excesswaveguide base material 22 is etched away by conventional etchingmethods to form waveguide core 22 a, with side walls 34, underphotoresist mask 61 (FIG. 2( d)). Then the photoresist mask is etchedaway (FIG. 2( e)). To complete fabrication of waveguide 10, suitableside boundary material 30 and upper boundary material 32 are depositedaround waveguide core 22 a (FIG. 2( f)). The etching process thatremoved the excess waveguide base material 22 resulted in irregularitiesin the side walls 34 of the waveguide core that increase interfacescattering losses for light signals transmitted in the waveguide core.

Also known are optical waveguides formed from material diffusionprocesses. For example, titanium may be selectively diffused intoregions of lithium niobate to form an optical waveguide wherein thediffused regions have a higher IOR than the non-diffused regions.

Therefore there is the need for an on-chip optical waveguide that can befabricated without the boundaries of the waveguide core being subjectedto photoresist etch damage and without the diffusion of a material intothe base waveguide material.

With respect to organosilicons that might serve as plasma depositedwaveguide material, despite intensive research on the plasma depositionof amorphous silicon from monosilane (SiH₄), there have been only a fewreports exploring the formation of Si—Si bonded polymers frommonosubstituted organosilanes. Haller reported an example of selectivedehydrogenative polymerization, but no photochemical studies weredescribed. See Hailer, Journal of the Electrochemical Society A, Vol.129, 1987, p. 180, and Inagaki and Hirao, Journal of Polymer Science A,Vol. 24, 1986, p. 595. Studies on the plasma chemistry of methylsilane(MeSiH₃) have involved higher radio-frequency powers and temperatureswhich promote formation of amorphous silicon carbide (SiC) rather thanreactive polymeric product. See Delpancke, Powers, Vandertop andSomorjai, Thin Solid Films, Vol. 202, 1991, p. 289. Low power plasmapolymerization of tetramethylsilane and related precursors has beenproposed to result in the formation of Si—C—Si linkages. See Wrobel andWertheimer, Plasma Deposition, Treatment and Etching of Polymers,Academic Press, New York, Chapter 3. Such materials lack sufficientabsorption in light above approximately 225 nm wavelength, but have beenstudied as far ultraviolet (193 nm wavelength) resists by Horn andassociates. See Horn, Pang and Rothschild, Journal of Vacuum ScienceTechnology B, Vol. 8, 1991, p. 1493. Polymer chemistry teaches the useof the basic silanes are insignificant as a monomer for polymerizationtype of polymer. Furthermore, polysiloxanes are differentiated from thebasic silanes, and contrasted as being very important in terms ofmonomers for polymerization. See Stevens, Malcom P., Polymer Chemistry,An Introduction, Addison-Wesley Publishing Co., 1975: p. 334.

Work has been reported on the synthesis of soluble poly-alkylsilynenetwork polymers ([SiR]_(n)) which exhibit intense ultravioletabsorption (associated with extended Si—Si bonding) and may bephoto-oxidatively patterned to give stable siloxane networks. SeeBianconi and Weidman, Journal of the American Chemical Society, Vol.110, 1988, p. 2341. Dry development is accomplished by selectiveanisotropic removal of unexposed material by chlorine or hydrobromicacid reactive ion etching. See Hornak, Weidman and Kwock, Journal ofApplied Physics, Vol. 67,1990, p. 2235, and Horn, Pang and Rothschild,Journal of Vacuum Science Technology B, Vol. 8, 1991, p. 1493. Theexposed, oxidized material may be removed by either wet or dry fluorinebased chemistry. Kunz and associates have shown that this makespolysilynes particularly effective as 193 nm wavelength photoresists.See Kunz, Bianconi, Horn, Paladugu, Shaver, Smith, and Freed,Proceedings of the Society of Photo-optical and InstrumentationEngineers, Vol. 218, 1991, p. 1466. The high absorbability and thewavelength limits photo-oxidation to the surface, eliminatingreflection, and the pattern is transferred through the remainder of thefilm during the reactive ion etch (RIE) development. Studies oforganosilicon hydride network materials containing reactive R—Si—Hmoieties have found that such high silicon compositions as[MeSiH_(0.5)]_(n) exhibit superior photosensitivity and function assingle layer photodefinable glass etch masks. See Weidman and Joshi, NewPhotodefinable Glass Etch Masks for Entirely Dry Photolithography:Plasma Deposited Organosilicon Hydride Polymers, Applied PhysicsLetters, Vol. 62, No. 4, 1993, p. 372. However, cost and availability ofthe exotic organosilicon feedstocks have significantly inhibited thetransfer of such photosensitive organosilicon hydride network materialsinto microcircuit fabrication. Further, films deposited from singlecomponent organosilicon feedstocks possess limited latitude inalteration of deposited film characteristics, such as the radiationfrequency of photosensitivity and selectivity during etch processes.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention is an optical element fabricatedfrom a selective photo-oxidation of a material formed from atwo-component plasma reaction in a substantially air-evacuated plasmachamber wherein the first component of the two-component reactioncomprises a non-carbon containing and non-oxygenated silicon donor, andthe second component comprises a non-silicon containing andnon-oxygenated organic precursor. The photo-oxidized material exhibitsan index of refraction that is lower than that of the non-photo-oxidizedmaterial to form an optical element that will alter a light signalpassing through the optical element.

Another aspect of the present invention is an optical waveguide formedfrom a selective photo-oxidation of a material formed from atwo-component plasma reaction in a substantially air-evacuated plasmachamber wherein the first component of the two-component reactioncomprises a non-carbon containing and non-oxygenated silicon donor, andthe second component comprises a non-silicon containing andnon-oxygenated organic precursor. In one application, thenon-photo-oxidized material forms the waveguide core and thephoto-oxidized material forms boundary walls of the waveguide corewithout the need for etching processes.

These and other aspects of the invention are set forth in thespecification and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, there is shown in thedrawings a form that is presently preferred; it being understood,however, that this invention is not limited to the precise arrangementsand instrumentalities shown.

FIG. 1 is a diagrammatic cross sectional view of a typical opticalwaveguide.

FIG. 2( a) through FIG. 2( f) are diagrammatic cross sectional viewsillustrating the process of forming an optical waveguide withconventional photoresist methods.

FIG. 3( a) through FIG. 3( e) are diagrammatic cross sectional viewsillustrating the process of forming one example of a plasma depositedoptical waveguide of the present invention.

FIG. 4 is a graph illustrating variability of the index of refraction ofthe plasma deposited optical waveguide material used in the presentinvention by selective exposure to varying dosages of radiatedelectromagnetic energy in the presence of oxygen

FIG. 5 is a graph illustrating variability of the index of refractionfor various samples of the plasma deposited optical waveguide materialused in the present invention by selective exposure to varying dosagesof radiated electromagnetic energy in the presence of oxygen.

FIG. 6 is a cross sectional view at section line A—A of the verticallystacked waveguide structure shown in FIG. 7.

FIG. 7 is a plan view of one example of a vertically stacked waveguidestructure of the present invention.

FIG. 8 is a cross sectional view at section line B—B of the verticallystacked waveguide structure shown in FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 3( a) through FIG. 3( e) illustrate one method of fabricating aplasma deposited optical waveguide 50 of the present invention. Bottomboundary material 52 is deposited on substrate 54 by any suitable method(FIG. 3( a)). For example, a bottom boundary material of silicondioxide, 500 nm thick and having an IOR of approximately 1.448, may beformed on a semiconductor grade silicon wafer by thermal oxidation. Thebottom boundary material serves as an optical barrier to a light signaltransmitted in the waveguide core and may be any material with an IORthat is different from that of the waveguide core material. In otherexamples of the invention, the bottom boundary material and substratemay be the same material.

The substrate with deposited bottom boundary material is fixed in aplasma deposition chamber as further described below. After air isevacuated from the chamber, a two-component plasma reaction, wherein thefirst component comprises a non-carbon containing and non-oxygenatedsilicon donor, and the second component comprises a non-siliconcontaining and non-oxygenated organic precursor, deposits aphotosensitive precursor waveguide material 59 on bottom boundarymaterial 52 as shown in FIG. 3( b). A non-limiting thickness for theprecursor waveguide material would be approximately 1,750 nm. When usingphotolithography, a suitable mask is fabricated to selectively exposethe region of the precursor waveguide material that will form the sideboundary material of the waveguide core (or while simultaneouslydefining the region of the precursor waveguide material that will formthe desired waveguide core) to suitable radiated electromagnetic energyin the presence of oxygen. For example, a non-limiting example of asuitable mask 62 is illustrated in FIG. 3( c). Mask 62 comprises apatterned chrome emulsion mask coating 63 deposited on a suitablesubstrate 64, such as quartz or a glass. A suitable source of radiatedenergy, in this example, UV light, is applied through the mask to theprecursor waveguide material. The chrome mask coating absorbs theradiated energy and the substrate allows the transmission of theradiated energy to the regions of the precursor waveguide material thatwill form side boundary material 59 a of the waveguide. While aprojection mask is illustrated in FIG. 3( c), a contact mask may also beused. Other non-limiting methods of photo-oxidation of the precursorwaveguide material includes the use of a gray scale photomask forphoto-oxidizing multiple regions of the precursor waveguide material todifferent levels (IORs) with a single exposure radiation dosage, or theuse of successive dosages with appropriate masking to gradually lowerthe IOR of one or more selected regions of the material. Further inmethods of applying other sources of radiated energy, such as e-beams orfocused scanning deep UV lasers, a mask may or may not be required.Photo-oxidation of the precursor waveguide material in the regions thatform the side boundary material will make its IOR lower than that of theremaining non-photo-oxidized precursor waveguide material that formswaveguide core 58. The actual cross sectional width of thephoto-oxidized side boundary material need only be of sufficient depthto effectively propagate a particular light signal transmitted by thewaveguide core. A suitable top boundary material 60, such as siliconoxide film deposited by a room temperature chemical vapor depositionprocess, is formed over the side boundary material and waveguide core tocomplete fabrication of waveguide 50 as shown in FIG. 3( e). As with thebottom boundary material, top boundary material 60 may be any materialwith an IOR that is different from (generally lower than) that of thewaveguide core material. The above process produces a waveguide withoutthe disadvantages associated with a photoresist, chemical or physicaletch, or diffusion process. The side boundary and top boundary materialscan be etched in a fluorine-based etchant so that vias can be providedfor any electrical connections.

The plasma-deposited photosensitive polymer used for precursor waveguidematerial 59 is produced by flowing a silicon donor and an organicprecursor into an evacuated plasma chamber, wherein the donor andprecursor react and deposit the precursor waveguide material on thebottom boundary material 52 (disposed on substrate 54 for this example,and referred to as “substrated bottom boundary material”) fixed in thechamber. Any plasma chamber with the following characteristics would besuitable for the process:

-   -   (1) hardware for evacuating the chamber to eliminate the        presence of oxygen;    -   (2) electrodes supplied with electrical energy to sustain the        plasma;    -   (3) hardware for flowing the silicon donor and organic precursor        through the plasma chamber at controlled flow pressures; and    -   (4) hardware for holding the substrated bottom boundary material        in position in the plasma chamber.

For the deposition of these particular materials, a Model DSN RoomTemperature Plasma Deposition System, which is available from IonicSystems (San Jose, Calif.), was used. This plasma chamber issubstantially as disclosed in U.S. Pat. No. 4,262,631, which isincorporated herein by reference. The ability to perform the plasmadeposition of the precursor waveguide material, and all subsequentwaveguide fabrication processes at room temperature, makes the plasmadeposited waveguide of the present invention particularly suitable foroptoelectronic applications. The plasma chamber was equipped with dualpower supplies of 2,500 W and 1,000 W that operated at 13.56 MHz. Theplasma chamber was vacuum pumped with an Edwards High VacuumInternational (Wilmington, Mass.) Model E2M-80 direct drive rotary vanepump. Flow pressures were monitored with an M K S Instruments, Inc.(Andover, Mass.) Series 220 BARATRON.

With use of the Model DSN Room Temperature Plasma Deposition System, thesubstrated bottom boundary material can be fixtured in the positivecolumn of the plasma discharge. This reduces the bombardment byenergetic species as there is no net charge density in the positivecolumn which reduces crosslinking in the deposited precursor waveguidematerial.

The materials used as silicon donor and organic precursor must be in agaseous or vapor state to achieve flow through the plasma chamber.Selection of materials for the silicon donor and organic precursor willbe dependent upon the desired characteristics of the precursor waveguidematerial, the cost of the materials, and how well-behaved the materialsare in the processing environment.

The material used as a silicon donor is a substantially non-carboncontaining and non-oxygenated silicon compound. Silicon hydrides, thatis, silanes (Si_(n)H_(2n+2)) are preferred. In one preferred embodimentof the invention, monosilane (SiH₄) is used as the silicon donor. Othersuitable source materials for silicon donors include disilane (Si₂H₆)and dichlorosilane (SiH₂Cl₂).

The material used as an organic precursor is a substantially non-siliconcontaining and non-oxygenated organic compound. In these preferredembodiments, ethylene (C₂H₄), methane (CH₄) and ethane (C₂H₆) are usedas gaseous organic precursors, and toluene (C₆H₅CH₃) is used as a liquidvapor donor. Other suitable sources for organic precursors broadlyinclude organic compounds such as alkanes, alkenes, alkynes, phenyls andaromatic hydrocarbons. Selective organic compounds may be blended toachieve an optimum organic precursor for a desired precursor waveguidematerial.

In selected embodiments, monosilane is used as the silicon donor, andethylene gas or toluene vapor is used as organic precursors to depositthe precursor waveguide material. Flow rates of monosilane have beenused in the range of 20 to 200 scc/min (preferably 25 to 35 scc/min),and organic precursors flowed at 100 to 300 scc/min (preferably 140 to180 scc/min). Pressure in the plasma chamber has been allowed to buildto 150 to 500 mtorr (preferably in the range of 180 to 300 mtorr). Powerfor deposition of the material has been applied in densities from 0.8 to15 mW/cc, with the optimum range being 8 to 10 mW/cc at 13.56 MHz. Theseoperating parameters will be understood by those skilled in the art astypical operating conditions, and not limiting the scope of theinvention.

The monosilane used was Semiconductor Grade Silane (SiH₄), which isavailable from Liquid Carbonic Industries Corp. (Oak Brook, Ill.).Organic precursors were 99.9% pure ethylene, supplied by Liquid CarbonicIndustries Corp., or ACS Certified Class 1B toluene, supplied by FisherChemicals (Fair Lawn, N.J.).

Selected organic precursor materials must have sufficient vaporpressure, with or without heating, to allow their introduction into theplasma chamber. This includes a variety of materials that can be eithera gas or liquid at standard temperature and pressure (STP). In mostcases, the exposure of a liquid organic precursor in a containmentvessel to the vacuum system will generate sufficient vapor flow to allowmany liquids, as well as gases, to be used with no operator exposure. Ifsufficient vapor pressure is not attained, the liquid donor may beheated slightly to increase its vapor pressure. For the processing ofthe precursor waveguide material in one preferred embodiment of theinvention, one gas at STP, ethylene, or one liquid at STP, toluene, isused as organic precursor. Toluene was selected due to its favorablevapor pressure, as well as its ultraviolet transmission characteristics.Neither the silicon donor nor the organic precursor can contain anappreciable amount of oxygen, since oxygen with ultraviolet exposurefrom the plasma during the deposition process would causephoto-oxidation of the silicon and degrade the photosensitivity of thedeposited precursor waveguide material.

A silicon donor that is substantially non-carbon and non-oxygencontaining inhibits the polymerization of the silicon donor with theorganic precursor during the plasma reaction. This promotes the encasingof plasma generated modified forms of the silicon donor that include(Si—H) and (Si—Si) low molecular weight fragments that are forming aself assembled composite film with nanometer scale silicon—silicon andsilicon-hydrogen particles or dots within an organic polymer matrixformed substantially from plasma-polymerization of the organicprecursor. Therefore, photo-oxidation is achieved primarily by theoxidation of the silicon within the interstitially situated modifiedforms of the silicon donor when the material is subjected to radiatedelectromagnetic energy, such as UV light, in the presence of oxygen.

For the monosilane/ethylene depositions, ethylene was supplied to aninlet port on the plasma chamber and controlled with a manual flowvalve. A vessel was used for the containment of liquid toluene for themonosilane/toluene depositions. The liquid nature of toluene at STPrequired the development of a method for the introduction of toluenevapors to the plasma chamber. A sample cylinder was obtained andthoroughly cleaned for the toluene introduction. After cleaning anddrying, the cylinder was attached to the deposition system and evacuatedto less that 10 mtorr. At this point, the valve on the sample cylinderwas closed and the cylinder removed from the system. A clean stainlesssteel tube was attached to the sample cylinder. The tube was submergedin a vessel of reagent grade toluene and the shut-off valve was opened.The vacuum inside the sample cylinder was used to draw the toluene intothe sample cylinder while introducing as little trapped gas as possible.After installation on the vacuum system, the shut-off valve was openedand the toluene was allowed to degas for fifteen minutes before anyplasma processing was attempted. Seasoning runs were performed for onehour before actual depositions were performed for the precursorwaveguide material.

A water bath was installed on the liquid toluene vapor source to assistin keeping a constant vapor pressure during the depositions. No heatingwas used in the bath, but the temperature held at 23° C.±1° C. duringdepositions. Pressure during depositions held constant within +5 mtorr.The effect of the evaporative cooling was minimal on the vapor pressureand flow of the liquid toluene donor. Flow from the vessel wascontrolled with a manually adjusted valve on the top of the containmentvessel. Initially, no attempt was made to either heat or hold the liquidvessel isothermal to reduce evaporative cooling, which would have animpact on the ability to maintain constant flow. However, pressureduring deposition was constantly monitored to determine if the flow ofthe toluene was dropping.

Initial depositions of the precursor waveguide material were performedwith the plasma chamber's depositor under manual control to easily varyand control deposition conditions. A monosilane flow rate of 50 scc/minwas used to establish a plasma chamber pressure with the monosilane, andthen varying amounts of organic precursors were flowed to achieve thedesired pressure increases. The ratio of the pressure of the organicprecursor to the pressure of the monosilane was used for monitoringduring the screening. Weight ratios of organic precursor to monosilaneof less than 1:4 and greater than 2.5:1 resulted in materials ofnegligible photosensitivity. For depositions useful for the fabricationof optical elements, weight ratios of organic precursor to monosilane of1:2 and 1:1 were chosen. In addition, for deposition, input power to theplasma chamber was varied between 200 W and 400 W.

It is preferable to separately flow the silicon donor and organicprecursor into the plasma chamber to enhance substantial uniformity ofthe plasma modified silicon donors within the resulting organic polymermatrix and prevent possible spontaneous pre-reactions. As understood bythose skilled in the art, silicon donors and organic precursors can bepremixed in a variety of ratios to ensure uniform componentdistribution, and reduce the cost and complexity of the piping andassociated hardware for gas introduction into the plasma chamber. Donorsand precursors can also be premixed or mixed in a manifold. Premixing ofthe silicon donor and organic precursor is acceptable but may requirestricter process control to achieve a substantially uniform distributionwithin the material. Hydrogen or an inert gas may be added to increaseuniformity due to its higher mobility.

As understood by those skilled in the art, a variety of depositionsystems may be used that operate at a wide variety of power levels andtypes, including radio frequency range (approximately 40 kHz) throughmicrowave, and electron cyclotron resonance systems operating in excessof 2 GHz. In the preferred embodiments, there is no substrated bottomboundary material heating involved, but the substrated bottom boundarymaterial can be heated or cooled during the deposition process toenhance the properties of the deposited materials. A wide variety ofpressures, from ultrahigh vacuum (less than 10⁻⁷ torr) up to andexceeding atmospheric pressure can be used. In the preferred plasmachamber, the substrated bottom boundary material floats electrically,but it can be grounded or powered.

As stated above, lithographic projection is used to selectively exposethe precursor waveguide material 59 to electromagnetic energy in thepresence of oxygen. Samples of the precursor waveguide material 59 thatwere prepared by the above processes were exposed to ultravioletradiation in the presence of oxygen from the air. Exposures wereperformed at low resolution using UVP, Inc. (Upland, Calif.) Model No.UVG-54 ultraviolet source for use at 254 nm wavelength. Exposures at 365nm wavelength were made using the same lamp housing with a UVP, Inc.Model No. 34-0034-01 ultraviolet source for use at 365 nm wavelength.Various masks were used for imaging. Photosensitivities were firstobserved after exposure to 254 nm wavelength deep ultraviolet (i.e., 280nm or less) with a simple contact mask. The precursor waveguide materialdeposited by the above disclosed processes had thicknesses ranging from0.08 to 0.15 μm. Table 1 illustrates deposition parameters for typicalsample depositions using the above process.

TABLE 1 Data for Sample Depositions Partial Pressure Resultant of theOrganic Depo- Compressive Precursor sition Stress in Sample OrganicRelative to Silane Power Rate Film Number Precursor (%) (W) (Å/sec)(Dynes/cm²) 1 Ethylene 50 400 0.82 2.7 × 10⁸ 2 Ethylene 50 200 0.71 8.3× 10⁷ 3 Ethylene 100 400 0.91 4.7 × 10⁸ 4 Ethylene 100 200 0.72 0.8 ×10⁸ 5 Toluene 50 400 0.85 3.3 × 10⁸ 6 Toluene 50 200 0.83 7.6 × 10⁷ 7Toluene 100 400 0.88 2.1 × 10⁸ 8 Toluene 100 200 0.88 9.8 × 10⁷

For the results in Table 1, the monosilane flow rate for all depositionswas 500.0 scc/min and the pressure from monosilane flow was 68 to 70mtorr. Stress measurements were made on bare 1,0,0 silicon wafers. Allexposures were made with light at 248 nm wavelength for exposure dosageof 600 mj/sq-cm. Deposited film thickness was 1500 Å.

Photo-oxidation as used in this specification is generally understood tobe accomplished by the exposure of a material to radiatedelectromagnetic energy in the presence of oxygen in air. Selectivephoto-oxidation is generally achieved by masking regions of the materialthat will not be photo-oxidized, with masking techniques known, forexample, in the art of photolithography. Generally, light energy isused, and more specifically, light in the ultraviolet end of the visibleelectromagnetic spectrum, typically recognized as from 200 nm to 400 nmis used for the radiated energy. It will be understood by those skilledin the art that other forms of radiant energy, above visible light inthe electromagnetic spectrum, such as x-rays, or gamma or alpharadiation, may be used. Furthermore, since oxygen in the air is theagent for oxidation, other concentrations of oxygen can be used,including oxygen that may diffuse through one or more layers ofmaterial.

Photosensitivity of the precursor waveguide material 59 was alsoexamined further into the visible region of the electromagneticspectrum. A single three-inch silicon wafer deposition was prepared by atwo-component reaction of monosilane and ethylene to determine exemplarynon-photo-oxidized waveguide core stoichiometry and photo-oxidized sideboundary material stoichiometry. The substrated bottom boundary layerwith deposited precursor waveguide material was quartered. One quarterwas exposed to 621 mj/sq-cm with light at 365 nm wavelength, and anotherquarter was exposed to 621 mj/sq-cm with light at 254 nm wavelength.

An elemental analysis was performed on portions of the two exposedsamples and one of the two remaining quarters of unexposed samples. Theresults are shown in Table 2, which indicates a 1:7 atom ratio ofsilicon to carbon for the unexposed samples, which could be used as awaveguide core.

TABLE 2 Elemental Analysis for Unexposed and Exposed Samples CarbonOxygen Fluorine Silicon Sample Type (%) (%) (%) (%) Unexposed 77 10 2.311 Exposed to light at 74 16 0 9.7 365 nm wavelength Exposed to light at67 22 2.2 9.2 254 nm wavelength

Portions of both exposed samples, and one of the quartered unexposedsamples, were submitted to Electron Spectroscopy for Chemical Analysis(ESCA). The ESCA analysis of the binding energies for the exposed (sideboundary material) and unexposed (waveguide core) samples provided theresults indicated in Tables 3A, 3B and 3C.

TABLE 3A ESCA Binding Energy Data for Unexposed Sample Peak SiO_(x)Assignments C—R C—OR O═C—OR C→C* C═O, Si—O C—F R—Si (RSi—O)_(n) (1 ≦ x ≦2) Binding 284.6 285.6 288.4 291.0 532.6 689.6 100.4 102.0 102.8 EnergyeV Unexposed 71 3.9 0.0 2.0 10 2.3 5.8 5.2 0.0 (Atom Percent)

TABLE 3B ESCA Binding Energy Data for Sample Exposed at 365 nm PeakSiO_(x) Assignments C—R C—OR O═C—OR C→C* C═O, Si—O C—F R—Si (RSi—O)_(n)(1 ≦ x ≦ 2) Binding 284.6 285.6 288.4 291.0 532.6 689.6 100.4 102.0102.8 Energy eV Exposed to 68 4.9 0.0 1.2 16 0.0 3.1 6.6 0.0 light at365 nm wavelength (Atom Percent)

TABLE 3C ESCA Binding Energy Data for Sample Exposed at 254 nm PeakSiO_(x) Assignments C—R C—OR O═C—OR C→C* C═O, Si—O C—F R—Si (RSi—O)_(n)(1 ≦ x ≦ 2) Binding 284.6 285.6 288.4 291.0 532.6 689.6 100.4 102.0102.8 Energy eV Exposed to 56 8.6 1.6 0.6 22 2.2 0.0 3.7 5.5 light at254 nm wavelength (Atom Percent)

The bonding information is drawn from high resolution scans of theelemental data and was used to examine the nature of the oxygen bondingas well. Atomic percentages are calculated for the included elements anddo not include hydrogen, of which a considerable amount is expected tobe present. The ESCA analysis represents approximately 100 Å of thesurface of the material.

The ESCA analysis indicates photo-oxidation with light at 254 nmwavelength by increased binding of oxygen at that wavelength whencompared to the unexposed sample. The analysis also showsphoto-oxidation with light at 365 nm wavelength not as prominent as thatwith light at 254 nm wavelength. As expected, the incorporation of boundoxygen into the exposed films causes a proportionate reduction in theamount of carbon and silicon present. The binding energy data, from thehigh resolution scans, provides more insight into the photoreaction atthe two frequencies. Peaks which show little significance, or are feltto be attributable to contamination, include the 689.6 eV bonds.However, significant trends did develop for the other represented bonds.Significantly, C—C, C—C*, C—H, Si—C, and Si—H bonds showed decreaseswith exposure. Furthermore, C—OC, C—OH, C═O, Si—O bonds showedconsistent increases with exposure to light at 365 and 254 nmwavelengths. It is also noted that with the exposure to light at 254 nmwavelength, all of the silicon present was bonded to oxygen in some formwith no remaining Si—C or Si—H bonds present. The 288.4 eV bond assignedto O═C—OC and O═C—OH are also present with the material exposed to lightat 254 nm wavelength, but not at 365 nm wavelength.

The binding energies assigned to C—R and R—Si are the correct energiesto be predominantly hydrogen bonds. Therefore, substantially no Si—Cbonding is apparent from the analysis for either the unexposed orexposed states. The lack of substantial silicon to carbon bonding isindicative of a film that is not a copolymer of silicon and ahydrocarbon, but comprises (Si—H) and (Si—Si) low molecular weightfragments interstitially situated within a substantially organic polymermatrix that does not contain an appreciable amount of silicon and doesnot exhibit highly photosensitive behavior. The results show thatsatisfactory photoreactivity was demonstrated with UV light at 254 nmand 365 nm wavelengths for the precursor waveguide material.

FIG. 4 graphically illustrates examples of the ability to vary the IORof the precursor waveguide material 59 by selectively exposing it toradiated electromagnetic energy of a suitable wavelength in the presenceof oxygen to form a photo-oxidized side boundary material 59 a that hasan IOR lower than that of the non-photo-oxidized waveguide core 58.

For the examples in FIG. 4, the precursor waveguide material is plasmadeposited from a two-component reaction wherein the silicon donor ismonosilane as specified above, and is maintained at a 50 scc/min flowrate for the deposition. The organic precursor is toluene, as specifiedabove, with a flow rate such that the toluene pressure rise is one-halfthe silane pressure rise (50% donor concentration). Initial chamberpressure for all depositions was less than 10 mtorr. Input power to theplasma chamber was 200 watts for the plasma deposition.

The section of the precursor waveguide material 59 that forms the sideboundary material 59 a was exposed to radiated electromagnetic energy,in this example, UV light with a wavelength of 248 nm, at varyingdosages. The resulting IOR at each dosage, measured by opticalellipsometry for a 632.8 nm wave, is set forth in Table 4 andillustrated in FIG. 4.

TABLE 4 Change in IOR for Varying Dosage of Radiated Energy ExposureExposure Dosage Index of (mj) Refraction 0 1.684 200 1.629 600 1.6041,200 1.587 1,800 1.583 2,400 1.576 3,600 1.571 4,800 1.570

Therefore, for the precursor waveguide material 59 in this non-limitingexample of the invention, a mask 62 was used to expose the region of theprecursor waveguide material 59 that would form side boundaries 59 awhile the waveguide core 58 was not exposed. From Table 4, thenon-exposed waveguide core 58 (0 exposure dosage) had a 1.684 IOR whilethe side boundary layers, if subjected to a 1,800 mj exposure dosage,would have an IOR of approximately 1.583. As indicated above, forsilicon oxide bottom and top boundary materials, the index of refractionwould be approximately 1.448. The data in FIG. 4 illustrates thecontrollable variation of the IOR in a plane of the precursor waveguidematerial or film by photo-oxidation of the film for construction andoptimization of waveguiding structures and optical signal manipulationstructures.

As further examples of the ability to vary the IOR of plasma depositedprecursor waveguide materials of the present invention, plasma depositedprecursor waveguide material was prepared on substrates of siliconsemiconductor wafers that were designated (Sample ID) as indicated inTable 5. For these plasma dispositions of precursor waveguide material,the silicon donor was monosilane and the organic precursor was eitherethylene (gas precursor in Table 5) or toluene (liquid precursor inTable 5). The pressure of the organic precursor indicated in the tableis relative to the pressure that established the monosilane flow rateindicated in the table. In other words, concentrations of the silicondonor and organic precursor for a particular deposition are related topartial pressures attributable to each component. For example, if theplasma chamber was started at 10 mtorr of pressure, and the monosilaneflow stabilized and gave 110 mtorr of pressure, the flow rate(concentration) of monosilane was responsible for 100 mtorr of pressure.If 50 percent concentration of the organic precursor was achieved, thenthe organic precursor flow rate (concentration) added an additional 50mtorr of pressure. Process parameters for the plasma deposition of theprecursor waveguide material on each substrate are listed in Table 5.

TABLE 5 Data for Plasma Deposition of Precursor Waveguide Material FlowRate Partial Pressure Input Power Duration of of the Organic to Plasmaof Sample Monosilane Precursor Relative Chamber Deposition ID (scc/min)to Monosilane (%) (W) (s) 1 50 50% (gas precursor) 200 2,200 3 50 50%(liquid precursor) 200 2,200 A 20 45% (gas precursor) 100 2,200 C 60 45%(gas precursor) 100 2,200 EE 50 30% (liquid precursor) 400 2,200

Quadrants of each wafer sample plasma deposited precursor waveguidematerial were photo-oxidized to varying degrees (including nophoto-oxidation—0 exposure time) by varying the exposure dosage to aradiated electromagnetic energy (in this example, UV light sourceoperating at 254 nm wavelength and with an energy density of 1 mj/s fromUVP, Inc. Model UVG-54) in the presence of oxygen, as indicated in Table6. IOR was measured in each quadrant by optical ellipsometry, and was asindicated in Table 6.

TABLE 6 Data for Sample Plasma Deposited Precursor Waveguide Materialwith Varying Radiation Exposures Exposure Dosage Sample Film ThicknessIndex Of Sample ID (mj) Quadrant (Å) Refraction 1 0 IV 1,016 1.949 150 I1,013 1.959 300 III 1,063 1.799 450 II 1,107 1.730 3 0 IV 1,009 1.669150 I 1,121 1.604 300 III 1,139 1.594 450 II 1,155 1.589 A 0 IV   7131.787 150 I   729 1.747 300 III   749 1.718 450 II   770 1.680 C 0 IV  387 2.718 150 I   439 1.966 300 III   484 1.713 450 II   540 1.654 EE0 IV 1,284 1.726 100 I 1,451 1.587 200 III 1,447 1.578 300 II 1,5601.543

FIG. 5 graphically illustrates the ranges of IOR that were achievablewith varying degrees of exposure for precursor waveguide materialsdeposited on sample ID 1, 3, A, C and EE.

It is believed that precursor waveguide materials with a lowphoto-sensitivity at extremely short wavelengths (i.e., less thanapproximately 250 nm) will provide superior material stabilityparticularly when silicon oxide is used as a top and bottom boundarysealing material for the waveguide core. Generally optoelectronicdevices operate at frequencies above 365 nm, so the IOR of waveguidecore material should not detrimentally decrease from photo-oxidation ofthe waveguide core material by light signals transmitted through thecore after the waveguide fabrication is complete. Low photo-sensitivityis generally defined as a plasma deposited precursor waveguide materialof the present invention that requires less than 100 mj of exposure toradiated electromagnetic energy with a wavelength of less thanapproximately 250 nm to achieve a complete IOR change for the material.That is, with this exposure dosage, the material will have decreased toapproximately its minimum possible IOR when subjected to this radiation.

The above examples illustrate a process of forming a plasma depositedwaveguide core with a substantially uniform IOR that is determined bythe IOR of a particular non-photo-oxidized precursor waveguide material,since, in the above examples, the side boundaries are photo-oxidized andthe core is not. In other examples of the invention, selected regions ofthe core are photo-oxidized to form optical elements in the core withvarying IORs. For example, by forming a waveguide core from multiplelayers of precursor waveguide material, not only can the side boundarymaterial be photo-oxidized, but the waveguide core segment in each layerof precursor waveguide material can be selectively photo-oxidized toform a waveguide core that has a varied IOR along its cross sectionalheight. This is of particular advantage, for example, in fabricating lowloss, small bend radius optical elements or components of compactconstruction for the transmission of optical signals. The componentswould have a high refractive index contrast (relative difference in IORof the core and boundary material or cladding) while allowing a lowerindex core in another location of the same device to enhance matchingthe index of the core of the waveguide to the core of a connectingoptical component, such as an optical fiber to provide a low lossfiber-to-chip interconnect.

Further localized optical elements may be formed within the base opticalmaterial used as the precursor waveguide material by selectivephoto-oxidizing regions of the material. For example, a quarter-waveplate may be formed by selectively photo-oxidizing regions of thewaveguide core. Radiated electromagnetic energy of a suitable frequencycan be selectively applied to local regions within the precursorwaveguide material, including the waveguide core, for example, with aphotolithographic tool, by varied exposures or with a variable gradientmask, or selected points of the waveguide core, for example, with anelectronic beam or laser device. In addition to embedding opticalelements, an optical element fabricated by the plasma deposited methodof the present invention can have its IOR changed subsequent tofabrication by post-fabrication photo-oxidation to rework or tune theoptical element. For example, an arrayed waveguide grating fabricated bythe plasma deposited method of the present invention having multipleplanes of precursor waveguide material photo-oxidized to achievedifferent IORs in each plane, can have a particular plane furtheroxidized after fabrication to alter its IOR so that the componentoptimally performs in a given application.

FIG. 6 through FIG. 8 illustrate a further application of the plasmadeposited waveguide of the present invention wherein a verticallystacked, multiple waveguide core, plasma deposited waveguide structure70 is used as a low loss optical multiplexer/demultiplexer. Referring toFIG. 6, substrate 71 can be any suitable material, such as semiconductorgrade silicon. Bottom boundary material 72, such as, but not limited to,silicon oxide, is deposited on substrate 71 by any suitable method.First precursor waveguide material, which is the first precursorwaveguide material layer forming the waveguide structure, is depositedon the bottom boundary material by a two-component plasma depositionprocess of the present invention. The layer of first precursor waveguidematerial is then selectively photo-oxidized by exposure to suitableradiated electromagnetic energy in the presence of oxygen to form firstside boundaries 73 a and 73 b around first waveguide core 74 a. A firstradiation barrier layer 75 a is then deposited over the first sideboundaries and first waveguide core. A second precursor waveguidematerial is deposited over the first radiation barrier by thetwo-component plasma deposition process. The layer of second precursorwaveguide material is then selectively photo-oxidized by exposure tosuitable radiated electromagnetic energy in the presence of oxygen toform second side boundaries 73 c and 73 d around second waveguide core74 b and third waveguide core 74 c, respectively. Either the second orthird waveguide core may be as-deposited waveguide base material, whilethe other is selectively photo-oxidized to produce a waveguide core withan IOR that is less than that for the other waveguide core, and greaterthan that of its bounding second side boundary. A second radiationbarrier layer 75 b is then deposited over the second side boundaries,and second and third waveguide cores. A third precursor waveguidematerial is deposited over the second radiation barrier by thetwo-component plasma deposition process. The layer of third precursorwaveguide material is then selectively photo-oxidized by selectiveexposure to suitable radiated electromagnetic energy in the presence ofoxygen to form third side boundary layers 73 e and 73 f around fourthwaveguide core 74 d and fifth waveguide core 74 e, respectively. Thethird side boundaries, and fourth or fifth waveguide cores can then beselectively photo-oxidized by a process similar to that for the secondside boundaries, and second or third waveguide cores, to achievewaveguide cores and boundaries with different indexes of refraction. Athird radiation barrier layer 75 c is then deposited over the third sideboundaries, and fourth and fifth waveguide cores. A fourth precursorwaveguide material layer, which is the last precursor waveguide materiallayer forming the waveguide structure, is deposited over the thirdradiation barrier layer by the two-component plasma deposition process,and the fourth precursor waveguide material layer is selectivelyphoto-oxidized by exposure to suitable radiated electromagnetic energyin the presence of oxygen to form fourth side boundaries 73 g and 73 haround sixth waveguide core 74 f. Finally a suitable top boundary layer76 is deposited over the fourth side boundary layers and the sixthwaveguide core.

While four plasma deposited waveguide core layers are used in the aboveexample of a vertically stacked, multiple waveguide core, plasmadeposited waveguide structure of the present invention, a minimum of twowaveguide core layers could be used to form selectively photo-oxidizedregions in each of the two layers that will delineate one or morewaveguide core regions and boundary regions in each of the two layers.

Each radiation barrier layer can be formed from a radiation absorbing orreflecting material, such as a plasma deposited organic polymer materialthat absorbs the radiation used, for example, UV light, or a sputterdeposited metal, such as aluminum, on a silicon oxide base layer.

For use of waveguide structure 70 as a multiplexer/demultiplexer, eachplasma deposited layer of precursor waveguide material is selected sothat each of the six waveguide cores making up the structure have aunique IOR that is selected to optimally transmit an optical signal ofone frequency in a combination of multiplexed optical signals. Toachieve this a different combination of silicon donor and/or organicprecursor, and/or plasma deposition process conditions, may be used toform a precursor waveguide material in each layer with a differentnon-photo-oxidized IOR. Then the side boundary regions and/or the coreregions in each layer can be selectively photo-oxidized to satisfy therequirements that the IORs of cores in a given layer are greater thanthe side boundary material adjacent to the core. Alternatively, a singlecombination of silicon donor and organic precursor may be plasmadeposited for all layers of precursor waveguide material. Then the IORof all side boundary layers and core regions may be selectively alteredby photo-oxidation to satisfy the requirements that the IORs of thecores in a given layer are greater than the side boundary materialadjacent to a core.

FIG. 6 diagrammatically illustrates in cross sectional elevational atsection line A—A in FIG. 7 an input to a vertically stacked, multiplewaveguide core plasma deposited waveguide structure 70 when used as ademultiplexer. Circle 80 (in dashed lines) represents the diameter of aglass fiber core of a single mode fiber optic cable 81 that is suitablycoupled to waveguide structure 70. A single mode glass fiber coregenerally has a diameter in the range of 8.3 to 10 micrometers. Theoptimum waveguide core cross sectional dimensions for an optical signalof 800-nm wavelength would be approximately 1.6 micrometers in heightand 4.0 micrometers in width. Forming each of the waveguide cores 74 athrough 74 f with cross sectional dimensions within this range wouldpermit optical coupling of the signal with all six waveguide cores.

If the fiber optic cable carried six multiplexed light signals ofdifferent frequencies that were optimally tuned for transmission in onlyone of the six waveguide cores, each of the six multiplexed lightsignals would be transmitted through only one of the six waveguidecores. As illustrated in FIG. 7, the six waveguide cores fan out throughstructure 70 by appropriate selective photo-oxidation patterning in eachlayer of precursor waveguide material. With this fan out pattern, anoptical component, such as a fiber optic cable, can be suitably coupledto each one of the six waveguide cores at the output of thedemultiplexer, diagrammatically illustrated in FIG. 8 in cross sectionalelevation at section line B—B in FIG. 7. As illustrated in FIG. 8,additional boundary regions 73 i and 73 j are formed by the fan outpattern and must be appropriately photo-oxidized.

The present invention of a two-component plasma deposited base opticalmaterial with an IOR adjustable over a range by selective exposure tosuitable radiated electromagnetic energy in the presence of oxygen maybe used to fabricate other optical elements wherein a splitting orcombining of optical signals of different frequencies (or colors) isdesired, for example, in prisms and diffraction gratings. Also aspreviously mentioned, although the precursor waveguide material isselectively photo-oxidized in regions that form the side boundaries ofthe waveguide core to form a waveguide having a core IOR greater thanthat of its boundaries, the precursor waveguide material may also beselectively photo-oxidized in the region that forms the core to form awaveguide having a core IOR less than that of its boundaries.

The foregoing examples do not limit the scope of the disclosedinvention. The scope of the disclosed invention is further set forth inthe appended claims.

1. An optical waveguide comprising: a bottom boundary material; aprecursor waveguide material deposited on the bottom boundary material,the precursor waveguide material formed from a two-component plasmareaction in a substantially air-evacuated plasma chamber, a firstcomponent of the two-component plasma reaction comprising a non-carboncontaining and non-oxygenated silicon donor, and a second component ofthe two-component plasma reaction comprising a non-silicon containingand non-oxygenated organic precursor, the precursor waveguide materialcomprising (Si—H) and (Si—Si) low molecular weight fragments in the formof particles generated by modified forms of the silicon donor in theplasma reaction, the (Si—H) and (Si—Si) particles interstitiallysituated within a substantially non-photosensitive organic polymermatrix formed from plasma-polymerization of the organic precursor, theprecursor waveguide material forming on the bottom boundary layer: awaveguide core; and a one or more side boundaries formed by selectivelyphoto-oxidizing a region of the precursor waveguide material adjacent tothe waveguide core by exposing the region of the precursor waveguidematerial to a radiated electromagnetic energy in the presence of oxygen,whereby primarily the silicon in the (Si—H) and (Si—Si) fragmentsoxidize to form the one or more side boundaries of the waveguide core;and a top boundary material formed over the precursor waveguidematerial.
 2. The optical waveguide of claim 1 wherein the secondcomponent of the two-component plasma reaction is selected from thegroup consisting of alkanes, alkenes, alkynes, phenyls and aromatichydrocarbons.
 3. The optical waveguide of claim 1 wherein the secondcomponent of the two-component plasma reaction is selected from thegroup consisting of ethylene, methane, ethane and toluene.
 4. Theoptical waveguide of claim 1 wherein the first component of thetwo-component plasma reaction is selected from the group consisting ofmonosilane, disilane and dichlorsilane.
 5. The optical waveguide ofclaim 4 wherein the second component of the two-component plasmareaction is selected from the group consisting of ethylene, methane,ethane and toluene.
 6. A vertically stacked, multiple waveguide core,plasma deposited waveguide structure comprising: an at least twowaveguide core layers, each of the at least two waveguide core layersformed from a two-component plasma reaction in a substantiallyair-evacuated plasma chamber, a first component of the two-componentplasma reaction comprising a non-carbon containing and non-oxygenatedsilicon donor, and a second component of the two-component plasmareaction comprising a non-silicon containing and non-oxygenated organicprecursor, each of the at least two waveguide core layers comprising(Si—H) and (Si—Si) low molecular weight fragments in the form ofparticles generated by modified forms of the silicon donor in the plasmareaction, the (Si—H) and (Si—Si) particles interstitially situatedwithin a substantially non-photosensitive organic polymer matrix formedfrom plasma-polymerization of the organic precursor, wherein an at leastone region of an each one of the at least two waveguide core layers isselectively photo-oxidized by exposing the at least one region to aradiated electromagnetic energy in the presence of oxygen wherebyprimarily the silicon in the (Si—H) and (Si—Si) fragments oxidize in theat least one region of each one of the at least two waveguide corelayers, the at least two waveguide core layers arranged in a stackhaving a first layer and a last layer; a barrier layer disposed betweenthe each one of the at least two waveguide core layers, the barrierlayer comprising a material for blocking transmission of the radiatedelectromagnetic energy; a bottom boundary material disposed over thefirst layer of the at least two waveguide core layers, the bottomboundary layer forming a first end layer of the plasma depositedwaveguide structure; and a top boundary material disposed over the lastlayer of the at least two waveguide core layers, the top boundarymaterial forming a second end layer of the plasma deposited waveguidestructure, whereby a light signal is selectively guided through each ofthe at least two waveguide core layers.
 7. The waveguide structure ofclaim 6 wherein the second component of the two-component plasmareaction is selected from the group consisting of alkanes, alkenes,alkynes, phenyls and aromatic hydrocarbons.
 8. The waveguide structureof claim 6 wherein the second component of the two-component plasmareaction is selected from the group consisting of ethylene, methane,ethane and toluene.
 9. The waveguide structure of claim 6 wherein thefirst component of the two-component plasma reaction is selected fromthe group consisting of monosilane, disilane and dichlorsilane.
 10. Thewaveguide structure of claim 9 wherein the second component of thetwo-component plasma reaction is selected from the group consisting ofethylene, methane, ethane and toluene.
 11. An optical waveguidecomprising: a bottom boundary material; a precursor waveguide materialdeposited on the bottom boundary material, the precursor waveguidematerial formed from a two-component plasma reaction in a substantiallyair-evacuated plasma chamber, a first component of the two-componentplasma reaction comprising a non-carbon containing and non-oxygenatedsilicon donor, and a second component of the two-component plasmareaction comprising a non-silicon containing and non-oxygenated organicprecursor, the precursor waveguide material comprising (Si—H) and(Si—Si) low molecular weight fragments in the form of particlesgenerated by modified forms of the silicon donor in the plasma reaction,the (Si—H) and (Si—Si) particles interstitially situated within asubstantially non-photosensitive organic polymer matrix formed fromplasma-polymerization of the organic precursor, the precursor waveguidematerial forming on the bottom boundary material: a side boundarymaterial; and a waveguide core formed by selectively photo-oxidizing aregion of the precursor waveguide material in the side boundary materialby exposing the region to a radiated electromagnetic energy in thepresence of oxygen whereby primarily the silicon in the (Si—H) and(Si—Si) fragments oxidize to form the waveguide core; and a top boundarymaterial formed over the precursor waveguide material.
 12. The opticalwaveguide of claim 11 wherein the second component of the two-componentplasma reaction is selected from the group consisting of alkanes,alkenes, alkynes, phenyls and aromatic hydrocarbons.
 13. The opticalwaveguide of claim 11 wherein the second component of the two-componentplasma reaction is selected from the group consisting of ethylene,methane, ethane and toluene.
 14. The optical waveguide of claim 11wherein the first component of the two-component plasma reaction isselected from the group consisting of monosilane, disilane anddichlorsilane.
 15. The optical waveguide of claim 14 wherein the secondcomponent of the two-component plasma reaction is selected from thegroup consisting of ethylene, methane, ethane and toluene.
 16. Anoptical waveguide comprising: a bottom boundary material; an at leasttwo layers of precursor waveguide material deposited on the bottomboundary material, each of the at least two layers of precursorwaveguide material formed from a two-component plasma reaction in asubstantially air-evacuated plasma chamber, a first component of thetwo-component plasma reaction comprising a non-carbon containing andnon-oxygenated silicon donor, and a second component of thetwo-component plasma reaction comprising a non-silicon containing andnon-oxygenated organic precursor, each of the at least two layers ofprecursor waveguide material comprising (Si—H) and (Si—Si) low molecularweight fragments in the form of particles generated by modified forms ofthe silicon donor in the plasma reaction, the (Si—H) and (Si—Si)particles interstitially situated within a substantiallynon-photosensitive organic polymer matrix formed fromplasma-polymerization of the organic precursor, each of the at least twolayers of the precursor waveguide material comprising: a waveguide coreformed in at least one of the at least two layers of the precursorwaveguide material by selectively photo-oxidizing a first region of theprecursor waveguide material by exposing the first region of theprecursor waveguide material to a radiated electromagnetic energy in thepresence of oxygen whereby primarily the silicon in the (Si—H) and(Si—Si) fragments oxidize in the first region; and a one or more sideboundaries formed by selectively photo-oxidizing a second region of theprecursor waveguide material adjacent to the waveguide core by exposingthe second region of the precursor waveguide material to a radiatedelectromagnetic energy in the presence of oxygen, whereby primarily thesilicon in the (Si—H) and (Si—Si) fragments oxidize in the second regionto form the one or more side boundaries of the waveguide core; and a topboundary material formed over the at least two layers of precursorwaveguide material.
 17. The optical waveguide of claim 16 wherein thesecond component of the two-component plasma reaction is selected fromthe group consisting of alkanes, alkenes, alkynes, phenyls and aromatichydrocarbons.
 18. The optical waveguide of claim 16 wherein the firstcomponent of the two-component plasma reaction is selected from thegroup consisting of monosilane, disilane and dichlorsilane.
 19. Theoptical waveguide of claim 18 wherein the second component of thetwo-component plasma reaction is selected from the group consisting ofethylene, methane, ethane and toluene.